The invention involves a beam scanner for confocal microscopes with a rotary-drive disk as a base.
Beam scanners with disk-shaped, rotary-drive bases so-called disk scanners, have been used for several years in confocal microscopy. In the confocal microscopic imaging procedure only the structures of an object that are directly in the focal plane of the microscope objective are displayed. In a confocal optical arrangement the object is illuminated in the focal plane by a point light source. The light coming from the object is reflected by a beam splitter in the direction of a point light detector and detected. In this regard the point light source, point light detector, and the limited- diffraction light point on the object in the focal plane lie exactly in the optically conjugate points. Light that comes from outside the focal plane is not focussed sharply on the point light detector and hence is also not registered by the detector. For this reason there are no inputs from unfocussed parts of the object. Object parts that lie outside the focal plane are thus almost faded out. In practice very small pinhole apertures are used for the light source and point light detector. In order now to produce a three-dimensional image of an object, the light point must be guided relative to the object in an appropriate manner. One possibility for this is to use a multipoint scanner in the form of a Nipkow disk. This is a disk driven with an electric motor and having a grid of tiny apertures, so-called pinholes. A problem that occurs in practice in using the known disk scanner involves the light reflected back from the upper surface of the disk that falls on the eyepiece and irradiates or at least affects adversely the image of the object. Avoiding this kind of scattered light effects often requires substantial expenditure on apparatus. In addition, the use of a Nipkow disk as a beam scanner requires relatively expensive auxiliary optics because of the diffraction phenomena that occur at the pinhole apertures.